Is it a valid Deep Neural Network?
Yes, it is a very common practice to use some RNN when your input data is a sequence.
Besides, your network has some shape issue if your input data is 2D. You should, at least flatten your input data to a vector to be able to forward propagate to the dense layer, but instead of this use some kind of RNN. 
To the best of my knowledge, that dropout value doesn't good. It seems too low.